[Bug 296208] gpart(8): Backup/Create/Restore Differences

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=296208

Jose Luis Duran <jlduran@FreeBSD.org> changed:

           What    |Removed                     |Added
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 Attachment #272064|0                           |1
        is obsolete|                            |

--- Comment #3 from Jose Luis Duran <jlduran@FreeBSD.org> ---
Created attachment 272065
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=272065&action=edit
Fix the final LBA as well.

Compile the kernel with the patch:

/usr/src # make -j $(nproc) buildkernel
...
/usr/src # INSTKERNNAME=kernel.bz_296208 make -j $(nproc) installkernel
...
/usr/src # nextboot -k kernel.bz_296208
zfs bootenv is successfully written
/usr/src # shutdown -r now
...

Let's test:

# truncate -s 1G /tmp/md0.dat
# mdconfig -a -t vnode -f /tmp/md0.dat -u 0
# gpart create -s GPT /dev/md0
md0 created
# gpart add -a 4k -s 512K -t freebsd-boot -l gptboot0 md0
md0p1 added
# gpart add -a 4k -s 40M -t efi -l efiboot0 md0
md0p2 added
# gpart add -a 4k -t freebsd-zfs -l zfs0 md0
md0p3 added
# gpart show md0
=>     34  2097085  md0  GPT  (1.0G)
       34        6       - free -  (3.0K)
       40     1024    1  freebsd-boot  (512K)
     1064    81920    2  efi  (40M)
    82984  2014128    3  freebsd-zfs  (983M)
  2097112        7       - free -  (3.5K)

Note that our patch prevented gpart add -a 4k from setting the first usable LBA
= 40, and also the last usable LBA.

Now, lets backup/restore:

# truncate -s 1G /tmp/md1.dat
# mdconfig -a -t vnode -f /tmp/md1.dat -u 1
# gpart backup md0 | gpart restore md1
# gpart show md1
=>     34  2097085  md1  GPT  (1.0G)
       34        6       - free -  (3.0K)
       40     1024    1  freebsd-boot  (512K)
     1064    81920    2  efi  (40M)
    82984  2014128    3  freebsd-zfs  (983M)
  2097112        7       - free -  (3.5K)

I think ultimately, it is a matter of aesthetics.  The current behavior
produces a "cleaner" output.

Cleanup:

# mdconfig -d -u 0
# mdconfig -d -u 1
# rm -f /tmp/md0.dat /tmp/md1.dat

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